No information is available on the use of zenocutuzumab during breastfeeding. Because zenocutuzumab is a large protein molecule with a molecular weight of about 146,000 Da, the amount in milk is likely to be very low.[1] It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[2] Because no information is available on the use of zenocutuzumab during breastfeeding, an alternate drug may be preferred, especially while nursing a newborn or preterm infant. The manufacturer recommends that breastfeeding be discontinued during therapy and for 2 months after the last dose.